Telephone system



May 28, .1929. w. o. PASSMORE ET AL 1,714,724

' TELEPHONE SYSTEM Filed Dec. 17, 1927 annual: un

Iafilliam ggla by Fass'mar'a Ehar'les Edmund Beale Patented May 28,1929.

UNITED sr'rs WILLIAM OGLESBY PASSMORE, OF LIVERPOOL, AND CHARLES EDMUNDBEALE, OF LONDON, ENGLAND, ASSIGNORS 'IO- ASSOCIATED TELEPHONE ANDTELEGRAPH COMPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE.

TELEPHONE SYSTEM.

Application filed December 17, 1927, Serial No. 240,705, and in GreatBritain January 27, 1927.

The present invention relates to telephone systems and is moreparticularly concerned with such systems as employ switches ofthebackwardly hunting or finder type; for instance for connecting a callingsubscribers,

.line with a first numerical switch. It is well known that theoreticallythe use of finder switches for this purposeofiers considerable economiesas regards the amount of apparatus required when compared w1th thearrangement in which a forwardly hunting switch, a-

finder switch of large capacity, for instance 100 or 200 lines, whichshall require only a small number of controlling relays and which shalloperate at high speed.

According to one feature of the. invention a two-directional finderswitch is provided in which the operating magnets are supplied withtheir operating potential over the wiper of a distributor.

According to another feature of the invention in a two-directionalfinder switch both,

the operating magnets are adapted to be energized by current fed throughself-interrupt ing contacts independently .of wipers moved over bankcontacts by the operation of the respective magnets.

A further feature of the invention is that for controlling the operationof a two-directional finder switch two relays are provided each of whichis adapted to be energized over two different circuits from whichcurrent is supplied at different stages in the operation of the switch.

The invention will be better understood from the following descriptionof a preferred embodiment which should be taken in conjunction with theaccompanying drawing. It will be understood, however, that thearrangement shown and described is given by way of example only thatvarious modificaated.

tions could bemade in the circuit details without exceeding the scope ofthe invention.

Referring now to the drawing, the finder switch there showndiagrammatically is assumed to have access to 100 subscrib ers"lines,'

the individual equipment associated with one of which is also shown;This finder is one of a number of similar switches serving this group oflines, the finders being ass'ignedfor use. in turn underthe control ofthe distributorconr prising wipers 22 and 23 and magnet25.

Suppose" that the subscriber whose line term1nates' 1n conductors 1 and2removes his receiver to nitiate a call: a circuit is then completedoveral 'mature 12 and 13 and their back contacts for the line relay 4which accord ngly operates. At armatureb it connects ground to thepr1vate normal conductor extending to the connector banks so as tobusythe line therein, at armature 6 it prepares a circuit for the cut-oilrelay 10, at armature 7 it connects earth to contact'l l correspondingto the seventh level in the bank of the vertical wiper 2 1, and atarmature 8 completes a starting circuit over wiper 22 of thedistributor, which'circu'it extends over armaturej29 and its backcontact and lower, winding of relay The ground forenergizing relay 32 isalso eX- tended to the vertical magnet3O by wayof interrupter contactand accordingly this magnet commences to operate in a buzzerlike mannerto raise the wipers 182l step by step. XVhenthe vertical wiper 21 whichis the only one makingcontact at this time finds ground, for instance onthe contact 14, a cirv cu-it is completed for the upper winding'of relay26 and this relay is accordingly oper- Thereupon at armature 31 it opensan additional pointin the release magnet circuit-,'a t armature 27'closes another point in the circuit of the cut-off relay 10, at armature28 completes a locking circuit for itself to the starting ground sincewiper 21 will leave contact 14; J on th efirst rotary step, and at relay26, and at armature37 opens a po nt mthe circu t of the rotary magnet38.

armature 29 disconnects the vertical magnet and the lower winding ofrelay 32 and extends the operating earth to the rotary magnet 38.Accordingly, the vertical movement of the switch is stopped and as soonas relay 32 deenergizes the rotary magnet circuit is completed atarmature 37 over the rotary interrupter contact. Magnet 38 accordinglyoperates in the usual manner to rotate the wipers in search of the testcontact associated with a calling line in the level chosen,'thehuntingmotion now being controlled by test wiper 20. The calling line itwill be noted is rendered selectable in the bank of wiper owing to theoperation of armature 6, whereby a comparatively low resistance batteryconnection through the winding of relay 10 is made to contact 17. Whenwiper 20 encounters this contact or the contact of another calling linein the same level, the following circuit is completed: battery, relay10, front contact and armature 6, contact 17, wiper 20,

armature 27 and its front contact, upper winding of relay 32 to earth.Relays 10 and 32 both operate in this circuit, and the former atarmature 12 and 13 clears the calling line of its normal battery andground connections and at armature 11 includes the resistance 9 in itsown circuit so as to mark the line engaged to other finders switches.Relay 32 operates as previously described and is now elfective to openthe rotary magnet circuit and connect the speaking conductors through. Acircuit is accordingly completed for the line relay ot' the firstselector associated with the finder switch, and this in turn operatesits associated release relay. Ground is then con- 7 nected back to therelease trunk conductor 41 thus holding relay 26 up over its lowerwinding and also extending by Way of the cont-act engaged by wiper 23and said wiper and in-' terruptercontacts 24 to the magnet 25 of thedistributor. This accordingly operates in 7 known manner until wiper 23is moved into engagement with a contact which is not grounded, thuspi'esclecting a further finder for use by the next calling line. Linerelay 4 de-energ'izes when itscircuit is opened on the operation ofrelay l0 and at armature 5 substitutes earth through the upper windingof relay 32 for the previous direct connection; these contactscontrolled by armature 5 may be arranged to be make-before-break itthought necessary. At armature 6 the shortcircuit around resistance 9 isremoved, at armature 7 ground is removed from contact 14 to preventinterference with other finders,

and at armature 8 opens the starting circuit. Assuming, however, thatthere is some other line calling at this time earth will still beconnected to wiper 22 by the corresponding line'relay and, the nextfinder assigned for use will then be set in operation to connect withthe other calling line.

When the subscribers have finished their conversation they will replacetheir receivers, whereupon the relay supplying feed current willdeenergize and ground will be removed from the release trunk conductor41. Thereand the switch is returned to normal in the usual manner, whileupon the release ofrelay 10 all the apparatus individual to thesubscribers line is restored to normal.

In the case of an incoming call, when the line is seized, ground isconnected to conductor 3 fromthe connector in the usual manner and acircuit is then completed for relay 10. This operates as before and atarmatures' 12 and 13 disconnects line relay at so as to prevent a finderbeing started up, when the subscriber answers the call.

Preferably the tenth contact in the vertical bank is permanentlyconnected to ground as shown so that if the finder should'fail to find acalling line on any level it would be stopped on the 10th level andwould then cut in and rotate ofi' the bank to the 11th position where itcould be arranged to give a special alarm or automatically to release.

It will be appreciated that a finder switch of this type can be arrangedwithout difiiculty to deal with a group of 200 subscribers lines inwhich case it would of course have an additional bank and set of wipersand an addiv tus. This arrangement has theadditional advantage that thehuntingtime which may be ofconsiderable importance is the same for aswitch of 200 lines capacity as for one of 100 lines capacity. This timeis reduced according to the present invention by arranging the magnets30 and 38 so that they interrupt their own circuits and are thus enabledto operate appreciably faster than it they worked in conjunction with aninterrupter relay, while at the same time the additional cost andmounting space of this relay are saved. This selfiinterruptingarrangement is rendered possible by specially designing the windings ofthe magnets sons to have a high resistance and by arranging thatpotential for operating them is not picked up from the contacts wipedover the test wiper but is provided locally, the hunting motioncontinuing until the magnet circuit is opened by the operationof thecorrespond ing testrelay. This arrangement obviates tory alternative tothe use of individual subscribers line switches.

What is claimed is:

1. In a telephone system, a line having an individual line equipmentassociated with it, a finder switch having access to said line, primaryand secondary driving magnets in said finder, and means responsive tothe initiation of a call on said line for extending a circuit from saidline equipment directly to said magnets in turn to operate said finderto establish a connection with said line.

2. In a telephone system, a line having an individual line equipmentassociated with it, a group of finder switches having access to, saidline, operating magnets in said finders, a distributor switch forallotting said finders for use one at a time, wipers on said distributorswitch, and means responsive to the initiation of a call on said linefor extending a circuit through one of said distributor switch wipers tosaid operating magnets to operate said finder to establish a connectionwith said line.

3. In a telephone system, a line having an individual line equipmentassociated with it, a finder switch having access to said line, selfinterrupting primary and secondary driving magnets in said finder, andmeans responsive to the initiation of a call on said line for extendinga circuit from said line equipment directly to said magnets in turn tooperate them to cause said finder to establish a connection with saidline.

4. In a telephone system, a finder switch having primary, secondary andrelease magnets, circuits for said magnets, a vertical control relay anda switching relay in said finder,

means for starting said finder by operating said primary magnet, meansfor energizing said switching relay during said primary operation toopen the circuit of said release mag net, and means for operating saidvertical control relay to stop the operation of said primary magnet, tostart the secondary magnet in operation and to deenergize said switchingrelay.

5. In a telephone system, a finder switch having primary, secondary andrelease magnets, circuits for said magnets, a vertical control relay,and a switching relay in said finder, means for starting said finder byoperating said primary magnet, means for energizing said switching relayduring said primary operation to open the circuit of said releasemagnet, means for operating said vertical control relay to stop theoperation of said primary magnet, to start the secondary magnet inoperation and to deenergize said switching relay, and meansforsubsequently reenergizing said switching relay to establish a,

connection through said finder switch. 6. In a telephone system, afinder switch having primary, secondary and release magnets, circuitsfor said magnets, a vertical cone trol relay and a switching relay insaid finder, means for starting said finder by operating said primarymagnet, means for energizing said switching relay during said primaryoperation to open the circuit of said release magnet, means foroperating said vertical control relay to stop the operation of saidprimary magnet, to open a further point in the circuit of said releasemagnet, to start the secondary magnet and to deenergize said switchingrelay and means for subsequently V reenergizing said switching relay tostop said secondary magnet and to establish a connection through saidfinder switch.

7. In a telephone system, a group of subscribers lines, afinder switchhaving access to said lines, a primary bank and a secondary bank on saidfinder, means responsive to the initiation of a call on one of saidlines for placing a ground potential on the primary bank and a batterypotential on the secondary bank to designate said line, two operatingmagnets and two relays in said finder means also responsive to theinitiation of said call for operating one of said operating magnets andthe first of saidrelays to start said finder, means including saidground on said pri mary bank for energizing the second of said relaysthereby stopping said first operating magnet and deenergizing said firstrelay to.

start the other of said operating magnets, and means including saidbattery potential on the secondary bank for reenergizing said firstrelay to stop said other operating magnet and to establish a connectionfrom said finder to said calling line.

8. In a telephone system, a line having a line and cutoff relayassociated therewith, a finder having access to said line, a switchthrough relay in said finder, means for start ing said finder responsiveto the initiation of a call on said line, means for energizing saidswitch through relay and cutoif relay in a series circuit to stop saidfinder and establish a connection with said line, and means in saidfinder controlled over said connection for breaking said series circuitto restore said finder and line to normal.

In witness whereof, I hereunto subscribe my.

name this 25th day of November, A. D. 1927.

CHARLES EDMUND BEALE.

